The solvation structure and dynamics of ions in aqueous N-methylacetamide (NMA) solutions are calculated using classical molecular dynamics simulations. Our results are analyzed in terms of varying composition ranging from pure NMA to pure water. We also examined the effect of varying water content on the structure and dynamics of a neutral solute. Altogether we have simulated 38 different systems in the present work. It is found that water molecules have preference over NMA for the ions irrespective of their charge and size, whereas the neutral solute is preferably solvated by methyl groups of NMA. The calculated self-diffusion coefficient values show comparatively slower dynamics for ions than the neutral solute which can be attributed to the stronger solvation of ions in aqueous NMA mixtures. Various dynamical properties associated with translational and rotational motion of solvents are also calculated, and similar slower dynamics of solvents is observed which can be attributed to the enhanced stability of the hydrogen bonds and formation of interspecies complexes in the mixtures.

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The development of engineered bone tissue, as a promising alternative to the conventional bone grafts, is not rewarding yet and remained challenging. Thus, attempts have been made in the present study to synthesize polyelectrolyte complex (PEC) scaffolds by blending of chitosan (CS) to silk fibroin (SF) derived from non-mulberry silkworm (Antheraea pernyi) at three different pH (5.0, 6.0, and 7.0), and characterize in terms of morphology, ultrastructure and mechanical properties with SEM, FTIR, XRD and tensile strength analyses. The prepared PEC scaffolds showed mean pore size of 130 µm as revealed by SEM analysis and comparatively higher compressive strength. The findings of in vitro cytocompatibility, in vivo biocompatibility and osteogenic markers (genes/proteins) analysis suggested that the PECs blended at pH 7.0 showed greater stability and enhanced growth and osteogenic differentiation capability of human mesenchymal stem cells (MSCs). To aid our understanding of protein-polyion binding mechanisms, we employed a molecular docking and simulation study of SF macrodomains and CS oligomer using Schrödinger 14 and GROMACS (GROningen Machine for Chemical Simulations) software. The study involved analytical techniques for macromolecular solution characterization and theoretical simulations based on molecular dynamics. The computational studies confirmed the presence of integral RGD sequence that played a vital role in superior cell-attachment, proliferation and osteogenic differentiation of MSCs grown on the developed SF-CS PEC scaffolds.

The structure and dynamical properties of liquid N-methylacetamides (NMA) are calculated at five different temperatures and at four different pressures using classical molecular dynamics simulations. Our results are analyzed in terms of pressure-induced changes in structural properties by investigating the radial distribution functions of different atoms in NMA molecule. It is found that the first peak and also the second peak of C-O and N-H are well defined even at higher temperature and pressure. It is also observed that the number of hydrogen bonds increase with application of pressure at a given temperature. On the other hand, the calculated hydrogen bond energy (E(HB)) shows that the stability of hydrogen bond decreases with increasing of pressure and temperature. Various dynamical properties associated with translational and rotational motion of neat NMA are calculated and the self-diffusion coefficient of NMA is found to be in excellent agreement with the experiment and the behavior is non-Arrhenius at low temperatures with application of pressures. The single particle orientational relaxation time for dipole vector and N-C vector are also calculated and it is found that the orientational relaxation time follows Arrhenius behavior with a variation of temperature and pressure.

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